Protein heterogeneity can be caused by a range of post-translational modifications. Protein heterogeneity often results from different types of post-translational modifications, including carboxylation, hydroxylation, proteolytic processing, sulfation, and glycosylation, the latter of which is the most common modification (Walsh and Jefferis (2006) Nat Biotech 24(10): 1241). Post-translational modifications can potentially affect product production levels (by influencing, for example, the degree of proper protein folding), stability, and a range of pharmacokinetic and pharmacodynamic parameters, as well as safety and immunogenicity. Post-translational modifications of therapeutic biologics, or protein-based biopharmaceuticals, may affect protein properties relevant to their therapeutic application.
N and/or C-terminal heterogeneity is an example of protein heterogeneity which must be considered in the manufacture of protein-based biopharmaceuticals. N-terminal heterogeneity results from proteolytic processing at the amino terminal portion of the protein, where such processing may result in a population of proteins having different sizes. Variations in N-terminal proteolysis may occur in proteins comprising a signal sequence. In addition, N-terminal glutamine residues can undergo spontaneous cyclization to form pyroglutamic acid. Thus, obtaining a homogenous population of proteins which can be used for therapeutic purposes often presents a challenge.
Lymphotoxin beta receptor (LTBR) is a member of the tumor necrosis factor receptor (TNFR) family. The receptor is expressed on the surface of cells in the parenchyma and stroma of most lymphoid organs but is absent on T- and B-lymphocytes. Signaling through LTBR by the LTα/β heterotrimer (LT) is important during lymphoid development. LTBR is also known to bind the ligand LIGHT (homologous to lymphotoxins, exhibits inducible expression, and competes with herpes simplex virus glycoprotein D for HVEM, a receptor expressed by T lymphocytes), which has been implicated in T-cell driven events, both in the periphery and in the thymus. LT and LIGHT are expressed on the surface of activated lymphocytes. Blocking the LT pathway with a soluble decoy LTBR has been shown to be effective to treat autoimmune disease in various animal models.
The development of soluble forms of LTBR having reduced heterogeneity and optimal dosing regimens for administration of these molecules would be of great benefit.